Quiz 3 Lecture 4

Question 1

What is a community?

Answer 1

All interacting populations in a habitat, has strong and weak interactions, emergent properties, internal structure of communities, and guilds

Question 2

What are the strong and weak interactions in a community?

Answer 2

strong- predator and prey interactions
weak- indirect competition

Question 3

What are the emergent properties in a community?

Answer 3

for ex species 1 eats species 2, but species 2 competes with species 3, therefore species 1 indirectly helps species 3

Question 4

What is a guild?

Answer 4

Organisms that are grouped together because they occupy a similar role in our food webs.

Question 5

In a foodweb is the biomass abundance fairly the same?

Answer 5

yes

Question 6

How does body mass and numerical abundance change throughout the foodweb?

Answer 6

The bottom is small organisms bu they are more abundant, top is large organisms less abundant

Question 7

What is done to figure out who eats who?

Answer 7

Direct observations of feeding
gut contents (hard cause organisms are digested)
laboratory feeding trials (put organisms with potential prey to see which one they go for)
stable isotope analysis

Question 8

What are the characteristics of stable isotope analysis?

Answer 8

Conservative
based on the origin of the substance
are ratios of carbon: 12C 13 C
ratios of nitrogen: 14N 15N
(12 and 14 more abundant, using mass spec see which isotope ratio present which can be an indictor of aten organisms, are used as tracers and measurements of natural conditions)

Question 9

Does carbon from terrestrial sources and carbon from aquatic sources have diff isotope ratios?

Answer 9

yes

Question 10

Given an example of how isotope ratios was used to see how a food chain was constructed?

Answer 10

There was a lake invaded by bass, used stable isotope ratios to see that after invasion by bass lake trout was consuming more zooplankton (isotopic ratios was more similar)

Question 11

What did the isotopic ratio indicate in the bass versus no bass example?

Answer 11

It showed that before lake trout went into littoral zone to prey fish and it’s diet was 60% prey fish and 40% zoo-plankton, but after the bass was added the lake trout then ate more zooplankton and shifted to the pelagic part of the lake as the bass outcompeted it for the prey fish, now it’s diet was 80% zooplankton

Question 12

What four things have we learned from aquatic food webs from stable isotopes?

Answer 12

terrestrial carbon is extremely important to aquatic food webs, 20-50% of zooplankton carbon is terrestrial (allonchtonous)
- the microbial loop is very important for food webs, starting with dissolved organic matter (most terrestrial matter is processed through this loop)
omnivory is the norm
most aquatic systems have 4 trophic levels (primary producer, primary consumer, planktivourous fish, top predator)

Question 13

What is functional diversity?

Answer 13

Functional diversity is a component of biodiversity that generally concerns the range of things that organisms do in communities and ecosystems

Question 14

How are functional groups different from guilds?

Answer 14

It is beyond the food web, functional groups are concerned with how a resource or any other ecological component is used by species to provide a ecosystem service/function

Question 15

What do scrapers do?

Answer 15

Scrape and eat algae and contribute to fine particulate organic matter

Question 16

What do shredders do?

Answer 16

They shred up coarse particulate organic matter into fine particulate organic matter

Question 17

What do collectors do?

Answer 17

consume fine particulate matter and produce it, they they get consumed by predators (feeder invertebrates)

Question 18

What is the river continuum concept?

Answer 18

Flowing water from headwaters to large rivers have set characteristics and changes in habitat at different stages which result in change sin which organisms we see.

Question 19

According to the RCC, what do we see in headwaters?

Answer 19

We see narrow streams and forest, with organic matter and lots of shade, there’s lots of coarse particulate organic matter as there’s leaves and twigs present, there is more respiration as it is not as productive (less sun), has more allochtonous carbon, more shredders and collectors present as compared to grazers and predators

Question 20

According to the RCC, what do we see in the midwaters? (stream order 4-5)?

Answer 20

We see more fine particulate matter, we see less shade so more photosynthesis then respiration, this results in more grazers to consume the algae produced by this photosynthesis and more collectors that eat this, the stream becomes less narrow, more autoonchous carbon

Question 21

According to the RCC what happens in lowest order streams? (4 to down)?

Answer 21

It’s a bigger faster deeper river so more organisms are in suspension, this limits photosynthesis as the water is more turbid causing PR ratio to be less than 1, mostly collectors are present here that filtrate fine organic matter and live in sediments. Also see zooplankton and phytoplankton.

Question 22

Where is the peak diversity of soluble organic compounds found?

Answer 22

Near headwater, then decrease as stream order goes down

Question 23

Where is the biotic diversity highest in a stream?

Answer 23

In the middle as the most functions can be performed here.

Question 24

Where is the largest temperature variation in the stream?

Answer 24

IN the midwaters, don’t see large variation in temp in headwaters and variation decreases past the midwaters

Question 25

How does the CPOM/FPOM raitio chnage as we move down a river?

Answer 25

Is high at headwaters but decreases as we move down as shredders have made it more fine and there’s not much input from the landscape

Question 26

When are periphyton grazers highest? Why?

Answer 26

Periphyton grazers are highest in mid stream orders, this is because benthic periphyton production is highest here

Question 27

Why are shredders and terrestrial coarse organic matter not present amongst desert streams?

Answer 27

Because they don’t have small cool streams covered by vegetation